Hyn Patty Posted January 21, 2022 Report Share Posted January 21, 2022 So I know there are a few of you UK members out there who work with bone china slip. There are hardly any Americans making and using it and I want to learn. I've picked up my raw materials and have a basic recipe of 50% bone ash, 25% Cornwall Stone, and 25% kaolin but finding out /more/ details isn't easy. The initial firing temps listed are super high at 1400 C (Orton cone 16), too high for my kilns that only go up to cone 10. I understand that adding fritware can lower the firing temps into a more workable range for me of say, 1250 C (2282 F or about cone 8). But I am not having any luck yet finding which fritware to use and how much. Anyone willing to make suggestions or have a bone china slip recipe with more detail that you might be willing to share? I currently have my bone china sculptures produced in England and I coudn't be happier with them except for the expense, and the fact that I may have a 1 to 2 year wait to get pieces done and shipped to me for glazing. I am blessed with a local supplier that carries everything I need - except again, I'm not certain /which/ kaolin is ideal for bone china slip. The one I got to try first is Grolleg English china clay. The Cornwall stone here is more orangey tan than expected and seems to be low in flourine, which I hope won't be a problem. Link to comment Share on other sites More sharing options...
Mark C. Posted January 21, 2022 Report Share Posted January 21, 2022 You read this I assume already https://www.porcelainbyantoinette.com/porcelain-clay-recipes.html#/ My friends have a family Castle near Cornwall (Fowey) where his sister lives and they visited a few years ago and I think they said the mine is still producing the stuff They are not potters by the way so the info is second hand The old stuff is different that the new stock. I have both-I am a bit fuzzy on those differences as rarely use any these past few decades. If I recall the old stock may be blueish in color? There are enough UK folks here to tell you what kaolins are used over there-maybe change your title asking for UK help in this quest so they can see it pop out Link to comment Share on other sites More sharing options...
PeterH Posted January 21, 2022 Report Share Posted January 21, 2022 You might find some useful bone china specific information in Slipcasting by Sasha Wardell Her site is at https://sashawardell.com/ Article by her Tempting Transparency https://tinyurl.com/mryx92z7 Link to comment Share on other sites More sharing options...
Hyn Patty Posted January 21, 2022 Author Report Share Posted January 21, 2022 I appreciate the input, thank you. Yes, I'm aware that the older Cornwall Stone used to have a much higher (but also more difficult to work with) flourine content that made it have a blue-green tint as seen in photos of Royal Worchester greenware. The new stuff has a much lower flourine content which supposedly actually makes it easier to use. I like double checking what I have read though - because there is always more to learn! As for changing the title of my post, I do not know how to do that yet. I've been on this forum a little while lurking but I rarely comment or post. Thank you both for your input. It is a great shame that I can't yet afford to simply come over the Pond and visit a while to learn hands on. That would be a holy grail of a trip for me and I certainly hope to, some day! Bone china has always facinated me and I've read just about everything about it I can lay eyes to but there is always more to find out. Which is what keeps life interesting! I will go check the offered links and see if there is anything new to add to my info compilation. Thank you - more input is still welcome! Link to comment Share on other sites More sharing options...
Hyn Patty Posted January 21, 2022 Author Report Share Posted January 21, 2022 Mark C wrote: 'You read this I assume already https://www.porcelainbyantoinette.com/porcelain-clay-recipes.html#/' Yes, I'm familiar with her recipes though her bone china ones seem to differ fairly dramatically from most of what I am seeing online. She admits she hasn't actually used or tested the bone china recipes herself. I still find the input helpful and interesting but no mention of fritware and I'm told real bone china has no feldspar in it so I hesitate to use her recipes. (I also clearly do not know how to quote other people's posts here, yet) Link to comment Share on other sites More sharing options...
Hyn Patty Posted January 21, 2022 Author Report Share Posted January 21, 2022 Peter H, your article you linked me to is great reading, thanks! I hadn't seen that one before. I've also made note of her website and I might reach out to her to see if she'll answer any of my questions. Hugely appreciated! Link to comment Share on other sites More sharing options...
glazenerd Posted January 21, 2022 Report Share Posted January 21, 2022 Hen Patty: Transluceny, rather it be bone china or porcelain carries the same basic principles: material purity, wall thickness, and heatwork. Metalloids (iron, magnesium, & titanium) affect translucent properties; primarily by changing how light is defracted as it passes through the clay wall. Ball clay contribute iron and magnesium: which is why they are not used in translucent recipes. Although kaolin is nearly pure of iron and magnesium: it does have titanium in various levels. EPK has high levels of titanium, and Grolleg has very little. Grolleg is the standard for translucent recipes for this reason: which is applicable to bone china. Translucent bodies also require clean plasticizers such as BentoneMA, or V-Gum T (as required), and ball clays are omitted from translucent bodies. Years back, I did some testing on bone china and fritware. From your question: you are landing in a mix of bone ware/ fritware hybrid. Selecting frit falls into the same category as metalloids: the frit has to be "clean." Many Frits have boron: which can cause cloudiness in a translucent body. Frit 3110 is relatively clean; and used in fritware. Frit begins to melt before cone 06; so as the cone temp climbs: added frit levels decline. A common fritware recipe at cone 04: 50% Grolleg, 30% frit 3110, and 20" silica. When I was testing bone china at cone 6- I replaced 12% of the bone ash with frit 3110. Got distracted by other pursuits, and never really finished my testing. Perhaps this will give you some direction? Link to comment Share on other sites More sharing options...
Hyn Patty Posted January 21, 2022 Author Report Share Posted January 21, 2022 Glazenerd, YES! This is exactly the sort of info I am seeking, thank you. Frit 3110 was reccommended to me to try - but no clue as to ratios. As I produce equine sculpture the translucency is less an issue. More whiteness from titanium is actually of benefit but I have been relatively unable to find out if I could use EPK for bone china or not. It is far more accessable to me locally than the Grolleg but it was the Grolleg that seemed to be used in English porcelain and maybe bone china. Been very difficult to refine that information. So I may pick up some EPK as well to try to compare batches and maybe even try a blend of the two. I know I can order Valentine's premixed powdered bone china slip - and I may do that but the freight charges on top of the base price is heartbreaking. If I do so, it would only be used to compare with my own slip making. So I am definitely motivated to learn to make my own and testing plenty. Porcelains I have used and am familiar with so the memory issue and lack of plasticity I am aware of, as well as having to prop it in the kiln for bisque firing using settles that I will also have to make. Porcelains however are too heavy and lack the strength and resiliancy that bone china has when parts need to be thin such as legs, manes and tails. As I have glazed a lot of English bone china I have come to love it. I already produce and ball mill my own custom earthenware slip for fine art sculpture casting, and used to use Seely's porcelain slip (that I still have some of) but bone china is definitely my big goal. It would save me a fortune if I can produce it in studio. Next week when I'm in Asheville, I'll swing by Highwater Clays and pick up some Frit 3110 to give that a try. 1400 C is not an option for me at this time so I have to work with what I have. I do not want to add more frit than I absolutely have to though. I need to avoid anything that might compromise the strength of the bone china as much as possible. I'll look into the BentoneMA and V-Gum T but again, I have no clue how much I would need to use in ratio to everything else. Not even a ball park guess. Link to comment Share on other sites More sharing options...
Min Posted January 21, 2022 Report Share Posted January 21, 2022 I have a Val Cushing Bone China cone 9 - 10 recipe, notes say it might only need a cone 8. Recipe for throwing below, leave out the macaloid if you test it for casting. I like that it has silica added, it's going to make it easier to fit glazes to. If you are looking for an even whiter clay I would give halloysite a try in place of the grolleg. Re Cornwall Stone there are recipes for mixing your own Cornwall Stone from common materials, I would be tempted to do this rather than using Cornwall Stone, avoids the whole fluorine gas issue. Val Cushing Bone China ^9-10 Grolleg 30 Cornwall Stone 20 Bone Ash 40 Silica 10 total 100 + Macaloid (aka Bentone MA) 2 * I edited your title to ask for any UK members help with this. Link to comment Share on other sites More sharing options...
Hyn Patty Posted January 21, 2022 Author Report Share Posted January 21, 2022 Outstanding, Min, thank you. Frit being silica, this gives me more comparisons and ratios to try. Yes, I don't think I'd want to add Bentone MA from what I am reading - since I'm not throwing. I'll look up making my own Cornwall Stone mixtures to try, as well. Oh wait, I already have that topic bookmarked. I forsee making a lot of small batches to test but if it works out, it'll be worth the effort. Thank you also for adjusting the title of my post! Link to comment Share on other sites More sharing options...
Hyn Patty Posted January 21, 2022 Author Report Share Posted January 21, 2022 This for example is a great article on making my own Cornwall Stone substitute and is facinating reading, should anyone else see my thread and also be interested in this topic to research. It was partly the basis for my learning about adding fritware to lower the firing temps initially: https://digitalfire.com/material/cornwall+stone Link to comment Share on other sites More sharing options...
Hyn Patty Posted January 21, 2022 Author Report Share Posted January 21, 2022 I will probably also order and try some of this https://digitalfire.com/material/h%26g+cornwall+stone as a safer and more reliable substitute for actual Cornwall Stone. I got real Cornwall Stone at my local distributer but the flourine content and the cost are concerns so I will be comparing batch tests. Link to comment Share on other sites More sharing options...
Min Posted January 21, 2022 Report Share Posted January 21, 2022 1 hour ago, Hyn Patty said: Frit being silica ? I’ve used this recipe for a Cornwall sub. I believe some suppliers have a ready mixed sub available too. Problem with using that is you won’t know the formula for it, could go with a theoretical one though. https://digitalfire.com/recipe/l3617a Link to comment Share on other sites More sharing options...
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